Repeater



Aug. 1o 1926.

J. S. JAMMER F1ed Feb. l, 1923 REPEATER 2 Sheets-Sheet 1 gl /fy V677 for.'

Jaco/ JT dam/77er by Am'/ J. S. JAMMER Aug. 10 1926. 1,595,100

REPEATER Filed Feb. 1 1923 2 Sheets-Sheet 2 /f/QZ ML/ ML2 J'acob 5 Jammer Patente-cl Aug. 10, 192.6.

UNITED STATES g l 1,595,100 PATENT orifice,

JACOB S. JAMMER, OF CUMBERLAND, MARYLAND, ASSIGNOR TO WESTERN ELEOTIO COMPANY, INCORPORATED, OF NEW YORK, N.

BEPEATEB.

Application led February This invention relates to repeaters and more particularly to high gain repeaters for commercial purposes.

In telephone repeater circuits, it is customaryto mount the amplifying apparatus comprised in a repeater circuit in compact form and to terminate the various parts of the circuit which require connection to apparatus outside of the repeater unit itself upon a terminal block where the several terminals are associated quite closely together. Consequently the input circuit terminals are ordinarily not far removed from the output circuit terminals. In the ordinary repeater heretofore used, this arrangement was entirely satisfactory but where large amplifications or gains are required, singing within the repeater results from the large potential and current dierences required between various parts of such acompact repeater structure.

Repeaters employing electron discharge devices as the amplifying elements are widely used in ordinary telephone systems and, especially in the United States, a more or less standardized repeater unit has been developed for this service. This unit has been designed for use upon ordinary long distance telephone lines and permits of satisfactory telephone transmission when inserted in the line at intervals of approximately 300 geographical miles. A new problem is presented, however, when these same lines are t0 be used for telephone and telegraph transmissions by means of carrier currents having frequencies many times those of ordinary voice frequencies. The attenuation of carrier frequencies resulting from' their transmission over long distance lines is very much greater than those of voice frequencies and therefore the problem of amplification is considerably more difficult of solution. The solution of this problem prior to the present invention consisted in locating the repeater stations closer to one another geographically.

This solution necessitated the construction of special repeater stations on transmission lines which were to be used both for voice and carrier frequencies.

This invention makes possible the elimination of these special repeater stations with a consequent increase in operating eiiiciency and reduction in operating cost. The same repeater attendants may be available for both the voice frequency repeaters and the 1, 192s. semi 1r. claus.

carrier 'current re eaters. Another important advantage.v the use of a high gain repeater according to this invention lies in the possible reduction in the number of repeater test stations. Ordinarily, the same test equipment can be used for a large number o at the same repeater station. Consequently, if all of the repeaters associated with a given line or plurality of lines assing through a given station, both voice fii'equency and carrier current, can be located at that station, an economy in testing equipment can be effected. A

An object of this invention is to increase the amplification or gain of which re eaters are capable. Another object is to mage possible a reduction in the number of repeater points in a commercial electrical transmission system by increasing the amplification of each repeater so as to span a greater geographical distance. Still another object is to supply polarizing potential for the input circuits of several electron discharge devices in a novel and efficient manner.

A feature of this invention is an operative repeater having a large amplification or high gain, which still retains the advantages of a unitary and compact structureof formerlower gain repeaters. Another feature is a two-way carrier current repeater having high gain characteristics wherein one group repeaters providing they are locatedy Y., A CORPORATION or Nnwyonx. l

of frequencies may be transmitted in one direction and a different group of frequencies in the other direction. A further feature is a carrier current repeater which spans the same geographical distance as the present voice frequency repeaters usedl on the same types of lines.

A typical arrangement of circuits for acarrier current repeaterV known and used previously to this invention is shown and described in P. A. Raibourn, April 18, 1922. This arrangement comprises a single amplifying structure in each branch of a two-way re1- peater having filter sections connected to both its input and output circuits between the two sections of the transmission line.

According to the present invention, a twoway carrier repeater may have the amplifying structures arranged in two stages, each of which is a unita-ry structure having input and output circuit terminals located on a single 'terminal block. The grouping lters Patent No. 1,413,357, issued to for separating oppositely directed transmissione for the Atwo oppositely directed branches consist of three elements one each located ahead ofbetween, andfollowingnthc two. amplifying structures.. An equalizer element may also be provided. All of the elements for a given branch may be mounted on vertical supports in the order indicated above having t e equalizer element placed between the first filter section and the first amplifying structure. The several elements are so interconnected that conductors carrying different values .of current or whlch are at widely different potentials are suiiciently separated physically to prevent feed back of energy from the output circuit of 'one amplifying device to its input circuit or to the input circuit of the preceding amplifying device so as .to prevent smging.

A. method of assoclatmg such a repeater `with ordinary telephone transmission line for multi lex o ration is described in an article hyp Messi); Colpitts and Blackwell entitled, Carrier current telephony .and telegraphy published in the Transactions of the American Institute of Electrlcal Engineers, volume XL, 1921. i

v The -novel features which are consldered characteristics of this invention are set forth with particularity in the appended claims. The invention itself, however, both as. to its organization and method of operation together with" urther objects and advantages thereof will best be understood by reference to the following descrlptlon taken in connection' with the accompanying drawlngs in which Fig. 1 illustrates a two-way carrier current high gain repeater. Fig. 2 shows a convenient arrangement o f the elements of the repeater of Fig. 1. F1gs. 3 and 4 illustrate certain details adapted for alternate use with the repeater of Fig. l.

-Referring now to Fig. 1, a two-way carrier current repeater 1s shown with two branches A and B connected for the two way transmission of diii'erent frequency range groups of carrier waves between transmission lines MU and ML2, as `explained in the Raibourn patent hereinbefore menioned., One group of frequencles is transmitted from line ML1 to line ML2 through branch A while another group of frequencies is transmitted inthe opposite direction from line ML2 to line LIU through branch B. The direction of transmission is 'indicated by arrows.

l an equalizer element Branch A comprises a filter section FAI, EA, an amplifying structure A1, a second vfilter section FA'f, an amplifying structure A2 and a third filter section FAS. The l adapted to pass vthe same range of frequencies. Preferably they oifer negligible attenuation .to current of the frequencies to be transmitted and very high attenuation to v with each other,

tersections are each words they are uniformly selective of tlo plurality of :frequencies to 'be transmitted. These filter sections :mayy be of the same general character as the well known band filters disclosed in patent to Campbell No. 1,227,113, May 22, 1917. Filters of lthis type consist in generalof a plurality of recurring sections having series and shunt re actances designed, according to well known laws, for the range of frequencies of the currents which the filters are to transmit.

he equalizer element EA is inserted to compensate for the .unequal attenuation of different frequencies by the transmission line MU. A network suitable for this apparatus is shown in Fig. 3 land comprises resistances 19 and 20 connected in series with a loop tuned circuit comprising inductance 21 and capacity 22. The inductance and capacity of this network are so proportioned that the loop circuit is resonant at substantially the highest frequency which is to be transmitted to the amplifying structures, consequently, this network provides a by-pass for the lower frequencies in proportlon 'to their remoteness from the frerlency to which the loop is tuned. The hig er frequencies are substantially unai'ectedand are tude upon the structure AIL' Another form of equalizer element EA, which for many purposes is the preferred form, is shown in Fig. 4. This form employs both a shunt section and a series section. The shunt section consists `of resistance 19 and inductance 48 connected in series with the loop tuned circuit comprising inductance 21 and capacity 22. The series section consistsy of three branches connected in parallel. Resistance 44 constitutes one branch; capacity 45, a second; and inductance 47 and capacity 46 connected in series a third. The loop tuned circuit 21-22 and the series tuned circuit 46-47 are each adjusted to resonance at approximately the highest frequency to be transmitted. The values of the other elements are so chosen that the transmitted current is substantiall proportional to the frequency thereof. The advantage of this form of equalizer element lies in its substantially uniform impedance, viewed from the line, to currents of all frequencies for which it is designed. The same forms of equalizer elements are suitable for element EB. The direction of transmission through these elements are indicated by dotted arrows. 'The amplifying structure A1 is somewhat similar to that disclosed in patent to E. H. Colpitts, No. 1,128,292, February 16, 1915, but it mustbe adapted to take care of the wide range of frequencies encountered in a carrier current system. stages of amplification It comprises two the first of which consists of electron discharge'devices 23 and 24 while the second stage consists of devices 25 and 26. Each pair of devices are connected in usb-pull relationship as explained in the Col)pitts and Blackwell article su ra. Plate current for the first stage is furnis ed by battery 27 in parallel through choke coils 28 and 29. Plate current for the second stage is sup lied by battery 30 in arallel through cho e coils 31 and 32. Po arizing potential for for the second stage by bats'imilar potential choke coil I36. Well known tery 35 through 37 and 38 is used etween stages. U

Energy from the line ML1 is impressed upon the input circuit of amplifying structure A1 by means of balanced potentiometer systems of the United States. Likewise,

39 and shielded inputv transformer 40. Output energy from amplifyin structure A1l is transmit-ted to a` secon filter section FA2 by means of shielded transformer 41.

The balanced potentiometer 39 has .two movable contacts, which are 'at all times equally distant from the ends of the resistance element. The potentials with res ect yto ground of the conductors connecte /these movable contacts are consequently equalized and a balancedy system resu ts.

The shielded transformers in this system, such as transformer 40, have a metallic shield between the line windings and the drop windings. windings which are connected directly or indirectly to the line, while'the drop windings are connected to apparatus, suc as the re atei' in this instance. By connecting this shield to ground a by-pass around the repeater is provided for currents which may result from foreign potentials between the line conductors and ground. Were it vnot for these shields these currents would fiidy way of the a path through the repeater b drop windcapacity between the linean ings.

A series parallel arrangement is used for heating the filaments from battery 42. Resistances 43 are employed to protect the lainents of the electron devices in either stage from an excessive iiow of current in case the filament of one of the electron devices in the same stage accidentally burns out.

The amplifying structure A2 also comrises a balanced arrangement of electron discharge devices such as described in the Colpitts patent hereinbefore mentioned. A single stage of amplification is employed however. `The two electron discharge devices 50 and 52 are connected in parallel `with cach other on one side, while discharge devices 51 and 53 are connected in parallel with ea'ch other on the other side. Plate -coil 58,l while grid polarizin the rst stage is furnished by the battery 33 through choke coil 34 andV The line windings are those v current Yfor all of these devices'is furnished b battery 54 through choke coils 55 and 56. (irrid polarizinpotential for devices 50 and 51 is supplied y battery 57' through choke I l potential for devices 52 and 53 is supplie by battery 59 through choke coils and 61. The filaments vare heated from batte 62 in a-mannersimilar to that of ampli ying structure A1. Energy is imgressed upon the amplifying structure A2 y shielded input transformer 63. Output energy from amplifying structure A2 is transmitted by shielded transformer 64.

The circuits of amplifying structures B andB2 are identical with those of amplifying structures A1 and Az respectively and need not further described in detail.

T he cathode heating current for. all of the devices may be obtained from a single source which practice is common in the telephone space current for all of the devices may be obtained from a single source. The polarizing potentials for the input circuits of all of the devices .may also be obtained from a single polarizing potential source. Reference may be made to patent to Clark No. 1,385,777, July 26, 1921, in this connection. In the arrangement of the lpresent invention a choke coil is included in each polarizing potential circuit. These choke coils offer hi h impedance to the currents to be ampli ed. T-he use of a' common source of polarizing potential reduces the plant upkeep to a minimum and enables ready location of faults in the supply source. These choke coils prevent cross-talk and singing which might otherwise result from the use of the common polarizing source.

In the amplifying structures A2 and B2 it is to be noted that the polarizing potentials for the separate pairs of grids are supplied through separate circuits. The pairs of grids are connected in parallel by means of condensers 65, 66. By this arrangement each grid may be given its proper polarizing potential and, if desired, the potential may be obtained from a source common to all of the devices. Previously when two electron devices which had their cathodes connected in series with each other were connected in parallel with respect to their input circuits, a supplemental polarizing potential source was connected into the gri circuit of one of the devices to compensate for the potential drop across the cathode of the other devices. Defective operation ot such repeaters, the cause of which was sometimes diiiicult to locate, would often be due to this supplement-al battery. This trouble is eliminated by the arrangement of this invention. v

Fig. 2 shows a convenient method of mounting'the several elements of Fig. 1 to provide a compact high ain repeater which will possess e'iiiciency wit lout singing. Corresponding parts of the two figures are designated by like reference characters. As shown, the several element-s of branch A are mounted one above the other on vertical supporting frames and 81.v The various elements are arranged from to to bottom in the order of their connection- 1n branch A from left to right. Similarly, the elements of branch B are mounted on vertical supporting members 81 and 82. elements are arranged from top to .bottom in the order of their connection in branch B from right to left. Transmission lines ML1 and ML2 are brought in from the top. A pair of conductors 5 are connected from the line ML1 to the input terminals of filter elev ment FA1. Another pair of conductors-l8 extends to the output terminals of filter element FBS.l A pair of conductors 12 connect the line ML2 to the input terminals of filter element FE1 while a pair of conductors 11 connect the lme ML2 to the output terminals of filter element FA". Connections between the several elements of branch A are made by conductors 6, 7, 8, 9 and 10. Slmilarly, connections between the elements o-f branch B are made by conductors 13, 14, 15, 16 and 17. -By means of this arrangement, conductors 18 may be physically separated from the interconnecting conductors 6, 7, 8, 9 and 10 and so reduce the possibility of singing by the repeater as a whole due to the feed back of energy from conductors 18 to conductors 7 and 9 which connect to the input terminals of amplifying structures A1 and A2. For the same reason, conductors 11 may be physically separated from conductors 14 and 16 of branch B. The arrangement also permits of a separation of conductors 7 and 10 and so prevents the feed back of 'energy from the output circuit of amplifying structure A2 to the input circuit of amplifying structure A1.

As previously explained, the individual "amplifying structures do not produce` suficient amplification or gain to cause singing within the individual structures, and according to this invention these several structures are so associated that any desired gain may be affected without singing.

In the Raibourn lpatent hereinbefore mentioned, transfer of energy from one branch to the other is prevented not only by the grouping) filters but al-so by a balanced connection etween the two branches. In the preferred embodiment of this invention as hereinbefore described, the balanced transformers are eliminated and singing around the repeater is preventedv solely by the grouping filters.

In a repeater arranged according to this invention, an amplification or gain compensating for the .attenuation of 45 miles of standard telephone cable can be accom- The several plished for'frequencies as high as 33,000 cycles per second. At the highest frequency `in the transmission range of branch A, for

1.5 miles; and in filter section ment. FA", 24.15 volts for amplifying structure A, and 2.8 volts for filter section FA". It is thus seen that if the entire amplification were obtained in one amplifying structure, the differences in voltage would amount to 28.65 volts.

While the invention described as embodied repeater,

has been specifically in a carrier current the invention is applicable to other repeaters. The scope of the invention is to lbe limited only by the appended claims.'

What is clained is: d l Y 1. In an amp ifying evice a p urality of three electrode-electron disdharge devices.

transmission employing high gain i connected'in parallel, a source of polarizing-v potential rfor each of said devices, and means I polarizing poten'- to confine the individual tials to the respective individual devices.

2. In a repeater, a plurality of electron discharge devices, a cathode, an anode, and an impedance controlling element for each of said devices, a source supplying current which is to be amplified, means to connect said impedance controlling elements in parallel with one another with respect to said source, means to connect said cathode and said impedance controlling elements to said source, an output circuit including said cathodes and anodes, means to Supply individual polarizing potential to each of said impedance controlling elements, and means to prevent the polarizing potential of each impedance controlling element from affecting that of any other impedance controlling element.

3. In a repeater, discharge devices, anode, and a grid source supplying current to be amplilied, means to connect said filamentary cathodes inseries with each other and to said source, means to connect said grids in parallel to said source, an output circuit including said iilamenta cathodesv and anodes, means to apply in ividual polarizing potentials to each of said grids and a condenser connected in circuit between said grids. h

"4. In .a repeater, a plurality of electron for each of said devices, av

discharge devices, a cathode, an anode, and an impedance controlling element for each of said devices, a sourcesupplying current to be amplified', means toconnect said cath odes in series and said impedance controlling elements in parallel respectively to said source, an output circuit including said cathodes and anodes, a source of polarizing potential common to all of said devices adapted to supply potentials of diferent values, independent circuits from said common source to each of said impedance controlling elements, and means to prevent the polarizing potential of each impedance controlling. element from aecting that of any other impedance controlling element.

5. In a repeater, a plurality of pairs of three electrode electron discharge devices, each pair of devices connected in push-pull arrangement with respect to each other and in parallel with said other pairs, a source of negative polarizing potential for each of said devices, and means to confine the polarizing potentials to respective individual pairs of devices.

6. In a repeater, a plurality of pairs of three electrode electron discharge devices, each pair of devices connected in push-pull arrangement with respect to each other and 80 in parallel with said other pairs, a source of negative polarizing potential for each of sai'd devices, means to confine the olarizin potentials to respective individual) pairs o devices, and a cho-ke coil offering high impedance to said current to be amplified connected in series with the individual polarizing potential source for each pair of devices.

7. A repeater station, a line incoming to said station and a line outgoing from said station, a plurality of amplifying structures each individually mounted, a plurality of filters each adapted to transmit with negligible attenuation the frequencies to be ampliied by said amplifying structures and to highly, attenuate all other frequencies, mounting means for the elements of said structures and said filters, said structures and said lters being so arranged on said mounting means that a lter is intermediate each two repeater elements, and connections between said repeater structures and said filters so arranged that the input connections of one repeater structure are separated from the output connections of an vadjacent repeater structure.

In Witness whereof, I hereunto subscribe my name this 26'day of January A D.,

JACOB S. JAMMER. 

